Dr. O. Sclimidt on CoccoUths and RJiahdoliths. 367 



PI. XVJ.I. fig. 13 shows a coccolith from the dorsal side, and 

 how the granular zone projects beyond the somewhat irregular 

 outlines of the shield. A monstrous shield-formation may, 

 however, occur, as in PL XVII. figs. 8 and 9, in which one 

 half of the shield is completely adherent, whilst the other has 

 grown out like a tongue. Rarely the margin of the shield is 

 notched and so swelled as to resemble the margin of the 

 granular zone, as in fig. 5. 



We come now to a very important, and, it seems to me, 

 quite unsettled question, namely that of the relation of the 

 coccoliths to the i^a^/i?/ J wts-protoplasm. Are they independent 

 organisms? or are they organs or parts oi Batliyhius'i In other 

 words, do they propagate themselves by passing through a 

 definite cycle of development, in which the Bathyhius-^xoio- 

 plasm serves them as a soil? or does their formation occur as 

 particles of the protoplasm? In the first place we have to 

 examine whether the doubling of the central granule, with 

 division of the surrounding parts, which is represented by 

 Hackel in a series of figm-es, leads to any reproduction. 

 Hackel simply states the fact, and says only that the elliptical 

 discoliths are often distinguished by having a double central 

 granule. But the importance of the central granule seems to 

 be by no means great, as it is frequently wanting in otherwise 

 perfectly regular and well-developed coccoliths. Many cor- 

 puscles with fissional processes or doublings occurring in 

 Bathyhius are either decidedly of a different nature or at least 

 doubtful. Thus PI. XVI. fig. 24 may be an Alga, and fig. 19 

 perhaps an Alga, but might also be a double central granule 

 with a correspondingly divided medullar ring. With regard 

 to corpuscles such as fig. 18, with a clear centre and turbid 

 periphery, if we consider them isolatedly, we can scarcely 

 make any supposition ; but compared with the not unfrequent 

 stages of coccoliths like fig. 20, they might be brought into 

 connexion therewith. As we may ascertain by placing it on 

 its edge, PI. XVI. fig. 20 is a decided coccolith with a perfect 

 dorsal shield ; the dark non-granular part represents the gra- 

 nular zone, and the clear spaces in it a divided medullar space 

 without central granules. PI. XVI. figs. 22, 23, is unique in 

 my knowledge. The structure and size leave no doubt that it 

 is a coccolith ; but the development in height is quite unusual. 

 The dorsal shield has become a capsule open above ; and the 

 two central granules appear deeply immersed in it. 



When I grasp the impression produced by numerous obser- 

 vations, compared with the facts of the reproduction of other 

 low organisms, the coccolith appears to me to he an independent 

 living creature. That nutrition and growth are performed by 



